Positive working photo-thermographic materials containing bi-imidazolyl compounds and reducing agents and the use thereof in color development

ABSTRACT

A RECORDING ELEMENT CARRYING A PHOTO-OXIDIZING BIIMIDAZOLYL COMPOUND IS CHEMICALLY REACTIVE CONTACT WITH A COMPOUND HAVING REDUCING PROPERTIES IN IMAGEWISE EXPOSED TO ACTIVATING RADIATION TO EFFECT REACTION BETWEEN THE BI-IMIDAZOLYL COMPOUND IN THE EXPOSES AREAS OF THE ELEMENT AND THE REDUCING COMPOUND TO DESTROY THEREDUCING PROPERTIES OF THE LATTER IN SUCH EXPOSED AREA AND THEREAFTER THE EXPOSED ELEMENT IS UNIFORMLY CONTACTED WITH AN IMAGE-FORMING COMPOUND WHICH IS REACTIVE ON HEATING WITH SAID REDUCING COMPOUND TO PRODUCE A DISTINCTIVE COLORATION AND HEATED SO AS TO PRODUCE BY SUCH REACTION A VISIBLE IMAGE CORRESPONDING TO THE UNEXPECTED AREAS OF THE RECORDING ELEMENT.

United States Patent US. Cl. 96-48 HD 19 Claims ABSTRACT OF THE DISCLOSURE A recording element carrying a photo-oxidizing biimidazolyl compound in chemically reactive contact with a compound having reducing properties is imagewise exposed to activating radiation to effect reaction between the bi-imidazolyl compound in .the exposed areas of the element and the reducing compound to destroy the reducing properties of the latter in such exposed areas and thereafter the exposed element is uniformly contacted with an image-forming compound which is reactive on heating with said reducing compound to produce a distinctive coloration and heated so as to produce by such reaction a visible image corresponding to the unexposed areas of the recording element.

The present invention relates to a photothermographic reproduction system and to materials used therefor.

In a Well known thermographic process a heat-sensitive copy sheet is used, which when heated beyond a certain temperature, turns black or dark coloured. In the process wherein such a copy sheet is used, the original that contains infrared light-absorbing image areas is exposed to infrared radiation while being in heat-conductive contact with the copy sheet. In correspondence with the image areas of the original the copy sheet reaches a temperature at which a coloured product is formed. So, in this process heat is accumulated image-wise in the original and transferred therefrom to the copy sheet.

As there is no neutralizing action of the reactive components still present in the non-heated portions of the recording layer, the copy paper will remain heat-sensitive and the image-containing copy paper will be blackened completely by overall heating. This characteristic and the fact that this process is limited to the copying of originals containing infrared radiation-absorbing image markings on an infrared radiation-reflecting background, make that process less attractive.

In order to find a solution for the disadvantages of said process a photothermographic process has been developed as described, e.g., in the US. patent specification 3,094,417 of Wesley R. Workmans, issued June 18, 1968.

In the latter process the difiiculty of colour-insensibility and of image stabilization of the copy sheet is solved. In said process light and heat energy are used and therefore it is called a dual one.

According to an embodiment of said process an intermediate U.V. light-sensitive sheet is used for the information-wise exposure. The intermediate sheet includes a volatilizable reductor that becomes transformed with the Patented May 22, 1973 aid of exposed photoreducible dye into a form that is unreactive for a reducible substance contained in a receptor sheet.

The present invention provides a novel photographic composition containing a photosensitive substance that by exposure to activating electromagnetic radiation destroys the reducing character of particular reducing compounds.

, Said photosensitive substance being a photo-oxidant is suited for being applied in a recording process, wherein in a first step information-wise modulated electromagnetic radiation is used to transform a transferable reducing agent into an unreactive species for a reducible substance, that is capable of yielding in a reaction with said reducing agent a product differing in colour from the reactants, and in a second step overall applied heat is used to transfer unmodified transferable reducing agent to a receptor layer or sheet containing said reducible substance.

The photosensitive compound used according to the present invention corresponds to the following general formula:

wherein:

each of R R and R stands for a carbocyclic or heterocyclic group with aromatic character and each dotted line circle stands for 4 delocalized electrons.

The R R and R groups having an aromatic character are e.g. a phenyl, biphenyl, naphthyl, furyl or thienyl group including said groups in substituted form. The substituents on said groups are restricted to substituents having no Zerewitinoff hydrogen atoms, in other words do not contain hydrogen atoms that are reactive with respect to methylmagnesium iodide.

Preferred bi-imidazolyl compounds correspond to the following general formula:

one]

wherein the valencies of the atoms in the imidazolyl rings, other than those through which the imidazolyl rings are joined, are satisfied by two conjugated intracyclic double bonds, and wherein A is a substituted phenyl radical of the formula:

wherein R represents a substituent not containing an active hydrogen atom and R R and R represent hydrogen or substituents free from active hydrogen atoms and where two of R R R and R in adjacent positionson the phenyl ring taken together may form a benzo ring, preferably the substituent or substituents ortho to the 4 imidazolyl radical having a sigma constant below 0.7; R R Rm R9 and B and D are phenyl groups which are unsubstituted or substituted with up to three substituents free from R R active hydrogen atoms, two of which, in adjacent positions 1 8 on the phenyl ring, may together form a benzo ring; 5 preferably at least one of the ortho positions in each of I J the phenyl groups B and D is unsubstituted. I The groups B and D can be alike or different as will be shown more fully below. A discussion and explanation C of the sigma value is given by H. H. Jaffe in Chem. Rev. 1 53, 191 (1953), particularly pages 219 to 223.

The substituents which are free from active hydrogen H atoms include alkyl, alkoxy, alkoxy-carbonyl, alkylthio, dialkylamino, dialkylcarbamoyl, dialkylsulphamoyl, alka- R R J noyloxy, N-alkylalkanamido, aryl, aryloxy, arylthio, 3 benzo, halo, and cyano groups. The alkyl substituents wherein R to R are alkyl groups, e.g. lower alkyl groups and the alkyl groups of the alkoxy substituents can be of 1 to 6 carbon atoms; alkoxy groups, e.g. alkoxy groups of any chain length, but are preferably lower alkyls such containing 1 to 6 carbon atoms; chlorine, bromine or as methyl, ethyl, propyl, butyl, isobutyl, sec.-butyl, tert.- fluorine atoms; or substituents on adjacent carbon atoms butyl, pentyl, isopentyl. The alkanoyl and alkanamido in the phenyl ring together forming a benzo ring, e.g. an substituents preferably contain from 1 to 6 carbon atoms, unsubstituted ring; with the proviso that at least one of i.e. ranging from formyl to capropyl and ranging from the ortho positions in each of the phenyl groups B and formamido to caproamide, respectively. The aryl groups D is unsubstituted. The dotted line circle stands'for 4 include phenyl, l-naphthyl, Z-naphthyl and the halo subdelocalized electrons. stituents include bromine, chlorine and fluorine. Representatives of the bi-imidazolyl compounds suited Particularly preferred compounds for use according to for being used according to the present invention are listed this invention are represented by the formula: hereinafter in Table I.

TABLE I Number of the compound R1 R; R;

1 o-Acetoxyphcnyl o-Acetoxyphenyl o-Acetoxyphenyl. 2. o-Benzylphenyl o-Benzylphenyl o-Benzylphenyl. 3 2, 3-benzo(1-naphthy1)phenyl 2, 3-benz (I-naphthyDphenyI- 2, 3-benzo(l-naphthyDphenyl. 4 2, 3-benzophenyl 2,3-benzophen l 2, B-benzophcnyl. 5. ,do p-Methoxyphenyl p-Methoxyphenyl. 6 3,4benzo-2-methoxy(2-[1-1neth0xy] 3, 4-benzo-2-methoxy(2[1methoxy] 3, 4-benzo-2-methoxy(2-[1-metlioxy] naphthyl)phenyl. naphthyDphenyl. naphthyDphenyl. 7 4, 5-benzo-2-methoxy(2-[3-meth0xy] 4, 5-benzo-2-methoxy(2-[3-methoxy] 4,5-benzo-2-methoxy(2-[3-n1eth0xy] naphthyl )phenyl. naphthyDphenyl. naphthyl)phenyl. 8 o-Benzylthlophenyl o-Benzylthiophenyl o-Benzylthiophenyl.

o-Bromophenyl-.... o-Bromophenyl o-Bromophenyl. do p-Bromophenyl.

o-Methoxyphenyl. 12 2-bromo-4-phenyl 2-bromo4-phenyl.

o-Butoxyphenyl o-Butoxyphenyl o-Butoxyphenyl.

o-tert.Butoxyphenyl o-tergButylphenyL. 0 N-butylacetamidephenyl o-Butylthiophenyl oButyryloxyphonyl o-tert.Butoxyphenyl o-Butylthiophenyl o-Butyryloxyphcnyl o-tert.Butoxyphenyl. o-tert.Butylphenyl. p-tert.Butylphenyl. N-butylacetamidephenyl. o-Butylthiophenyl. o-Butyryloxphenyl.

20 o-Chlorophenyl o-Chlor0pheny1 o-Chlorophenyl.

21 J p-ChlorophenyL. p-Chlorophenyl.

22 do 3, 4-diehlorophenyl- 3, 4-diehlorophenyl. 23 do m-PentyloxyphenyL. m-Pentyloxyphenyl. 24 dn dn 0,

25 do p-Propionyloxyphenyl. p-Propionyloxyphenyl. 26... 2-cl1loro-4-phenyL. 2-ehloro-4-phenyl. 27.- o-CyanophenyL-.- o-Cyanophenyl. 28.. do p-tert.Butylphenyl. 29-- p-Cyanophenyl. 30.. p-Methoxyphenyl.

zo (Q-phenanthry henyl 2, 3-dibromophenyl- 2, 4-dibromophenyl- 2, 6-dibutylpl1enyL-.. 2, 4-di-tert.butylpheny 2, 4-difluorophenyl 2, 3, t, 5-dibenzo(9-phenanthryl) phenyl. 2, 3-d1bromophenyl.

2, 4rdibromophenyl.

2, 6-dibuty1phenyl.

2, 4-di-tert.buty1phenyl.

37 0 p-Fluorophenyl p-Fluorophenyl.

38 o-Dibutylsulfarnylphenyl o-DibutylsulIamylphenyL- o-Dibutylsulfarnylphenyl. 39 2,4diehlorophenyl 2,4-dichlor0pheny1 2,4-dichlor0phenyl.

40 .do 0-Bromophenyl o-Bromophenyl.

p-Cyanophenyl.

4 2 6-dicyanophenyl 2,6fi1cyan0phenyl" 2,6-dicyanophenyl. 43 2 4-d1ethoxyphenyl 2,4-diethoxyphenyl 2,4-diethoxyphenyl. 44 o-Diethylsultamylphenyl o-Diethylsult'amylpheny o-Diethylsulfamylphenyl. 45.. 2,5-difiuorophenyl p-Cyanophenyl p-Cyanophenyl. 46 d0 (in D0. 47 2,8-dimethoxyphenyl 2,3-dimethoxypheny1 2,3-dimethoxy'pheny1. 48 2,4-dimethoxyphenyL. 2,4-dimethoxypheny1.-- 2,4dimethoxyphenyl.

do..-- o-Chlorophenyl. o-Chlorophenyl.

2,4'dimethoxyphenyl 2,4-dimethoxyphenyl.

do o-Methoxyphenyl. o-Methoxyphenyl. do p-MethoxyphenyL. p-Methoxyphenyl.

53 do m-Phenylthio m-Phenylthio. 54 o-Dimethylaminophenyl o-Dimethylaminophenyl. o-Dimethylaminophenyl. 55 do p-Dipentylaminophenyl p-Dipentylarninophenyl. 56 d0 o-Dipropylsulfamylphenyl. o-Dipropylsulfamylphenyl. 57 o-Dunethylcarbamylphenyl o-DimethylearbamylphenyL- o-Dimethylcarbamylphenyl. 58 2,4-d1naphthylthiophenyl. 2,4dinaphthylthiophenyl- 2,4dinaphthylthiophenyl. 59 2,4-dipentylphenyl 2,4'dipentylpheny1 2,4-dipentylphenyl. 60 do 3,4-benzo(2-naphthyl)phenyl 3,4-benzophenyl. 61 o-Dipentylarrunophenylo-Dipentylaminophenyl o-Dipentylaminophenyl. 62 2,4'd1propoxyphenyL .r 2,4dipropoxyphenyl. 2,4-dipropoxyphenyl. 63- do o-DiethylearbnmylphenyL. o-Diethylcarbamylphenyl. 64". oD1propylcarbaltmylphenylo-Dipropylcarbamylphenyl. o-Dipropylcarbamylphenyl.

65 o-Ethoxypheny o-Ethoxyphenyl o-Ethoxyphenyl.

TABLE IContin1ied Number of the compound R oEthoxyoarbonylphenyl..--.--

o-Ethylphenyl o-N-ethylbutyramido-pheny o-N-ethylpropylaminophenyl o-Ethoxycarbonylphenyl o-Ethylphenyl o-N-ethylbutyramjdo-phenyl..- o-N-ethylpropylaminophenyl a o-Ethoxycarbrinylphenyl.

. o-Ethylphen o-N-ethylbutyranudo-phenyl. o-N-ethylpropylaminophenyl.

o-Ethylthiophenyl o-Ethylthiophenyl o-EthylthiophenyL o-N-ethylvaleramido-phenyl p-tert.Pentylphenyl.. p-tert.Pent 1 hen l. 72 o-Fluorophenyl o-Fluorophenyl oFluoroph n yl. y 73 o-Methoxyphenyl o-Methoxyphenyl. 74., o-Methoxyphenyl do Do. 75.- do p-Chlorophenyl p-Chlorophenyl. 76 do p-MethoxyphenyL. p-Methoxyphenyl. 77 do o-Methoxyphenyl-. o-Methoxyphenyl. 78 do p-Methoxyphenyl. p-Methoxyphenyl. 79 do o-MethylthiophenyL- o-Methylthiophenyl. 80 I do p-Nitrophenyl p-Nitrophenyl. 81 do p-PhenylsulphonylphenyL- p-Phenylsulphonylphenyl. 82 o-Methoxyoarbonylphenyl o-Methoxycarbonylphenyl.. o-Methoxycarbonylphenyl. 83 do 3,4-benzophenyl 3,4'benzopheny1. 84.. o-Methoxyearbonylphenylp-N-ethylphenylsulphamyl. p-N-ethylphenylsulphnmyl. 85 2-methoxy-4-pheny1.. 2-methoxy4-phenyl Z-methoxy-tphenyl.

o-Methylphenyl... o-Methylphenyl o-Methylphenyl. .do p-Benzoyloxyphenyl p-Benzoyloxyphenyl. 88.. -N-methylacetamido-pheny1. o-N-ethylbutyramldophenyl. o-N-ethylbutyramidophenyl. o-N-methylacetamidophenyl o-N-methylacetomidophenyl. o-N-methylpropionamid0pheny1. o-N-methylpropionamidopheny1... 0-N-methylpropionamidopheny1.

o-Methylthiophenyl o-Methylthiophenyl o-Methylthiophenyl. o-l-naphthylphenyl. o-Phenoxyphenyl o-Phenoxyphenyl. o-2-naphthylphenyl. o-2-naphthylphenyl o-2-naphthy1phenyl. o-tertlentylphenyl. o-tert.Penty1pheny1 o-tert.Pentylphenyl. edentyloxyphenyl o-Pentyloxyphenyl o-Pentyloxyphenyl. 96 o-Pentyloxyoarbonylphenyl o-Pentyloxycarbonylphenyl.. o-Pentyloxycarbonylphenyl. 97 3,4-benzophenyl 3,4-benzophenyl. 98 o-Q-phenanthylphenyl p-Methoxyphenyl. p-Methoxyphenyl. o-Phenoxyphenyl o-Phenoxyphenyl.-.-. o-Phenoxyphenyl. 100 Jim 3,4,5-trimethoxyphenyl. 3,4,5-trimethoxyphenyl. 101.... o-Phenyl(2-biphenyl)- o-Phenyl(2-biphenyl) o-Phenyl(2-biphenyl). 102 o-Phenyl p-Methoxycarbonylpheny p-Methoxycarbonylphenyl. 103 -dn m-Pentyloxycarbonylpheny m-Pentyloxycarbouylphenyl. 104 do p-Peutyloxycarbonylphenyl Do. 105 .do p-Phenglp-Phenyl. 106.. o-Phenylthio.. p-l-nap thylthiophenyl p-l-naphthylthiophenyl. 107.. o-PropoxyphenyL- o-Propoxyphenyl o-Propoxyphenyl. 108.. 2,4,6-tribromopheny 2,4,6-tribrornophenyl. 2,4,6-tribromophenyl. 109.. 2,4,fi-tributylphenyl. 2,4,6-tr1butylphenyL. 2,4,6tributylphenyl. 110.- 2,3,5-triohlorophenyl- 2,3,5-trich1orophenyl. 2,3,5-trichlorophenyl. 111 2,4,6-triehloropheny1- 2,4,6-trichlorophenyl- 2,4,6-trichlorophenyl. 112 i do o-Butylthiophenyl... o-ButylthiophenyL 113 2,4,6-trlcyanophenyl p-Cyanophenyl p-Oyanophenyl. 114.. 2,4,6-triethoxyphenyl-.- 2,4,6-triethoxyphenyL. 2,4,6-triethoxyphenyl. 115.. -trimethoxyph nyl. 2,4,6-tr1methoxyphenyl. 2,4,6-t1imethoxyphenyl. 116-. 2,4,6-t1i-tert.pentylphenyl. 2,4,6-tert-tri.pentylpheny 2,4,6-tri-tert.pentylphenyl. 117.. 2,4,6'tripropoxypheny1..- 2,4,6-t1'ipropoxypheny1. 2, ,6tripropoxyphenyl. 118-. p-Chlorophenyl enyl Phenyl. 119-. p-Fluorophenyl. do Do. 120 Phenyl. p-Methoxyphenyl p-Methoxyphenyl. 121 3,4-dimethoxyphenyl Phenyl Phenyl. 122 5-aoenaphthylphen Do. 128 -dimethylaminopheny Do. 124 3-nitrophenyl. Do. 125 Phenyl. "do Do.

The last 8 compounds are CC isomers. CN isomers not listed in the Table I above and that are suited for being used according to the present invention have for R and R a phenyl group and for R a 4-chlorophenyl or 4-fluoropheny1 group.

The bi-imidazoly1 compounds can be prepared according to methods describedby Hayashi, C. S. in Bull. Chem. Soc., Japan, 33, 565 (1960), the French patent specification 1,351,818, filed Mar. 20, 1963 by Du Pont de Nemours, and the British patent specification 997,396, formula: filed Mar. 21, 1963 by Du Pont de Nemours. X

According to the preferably applied method the oxidative dimerisation is carried out in alkaline organic me- Z r I Z: dium by means of a cyanoferrate(III) such as potassium 0 cyanoferrate(III). According to that method normally a H 1,2-bi-imidazole (the O'N isomer) is obtaiied bu; somgwhereim times also the 1,1-, the 1,4'.-,'2,2--2,4- an 4,4- i-imi azoles (the latter being the 0-0 isomer) mixed with the X fgfi i gi gf gf Sulphur NH 1,2'-isomer. 65

For the purpose of the present invention it does not matter, however, which kind of isomer is used, as long A as it effects the desired photo-oxidation of the reducing and substance, contamed the mtermeqlate Sheet Z and Z each represent the necessary atoms to close Reducing compounds that-when mtunately mixed with 70 a carbocyclic aromatic ring benzene ring the bi-imidazolyl compounds-are capable to become oxieluding a substituted benzene ring. dized by means of the photo-exposed bi-imidazolyl com- Reducing compounds of class (1) are pounds belong to the class of organic compounds contain- (1) ing a Zerewitinoif hydrogen atom and more particularly, Jae-@ e.g., belong to one of the following classes: 75

Reducing compoundsof class (A) are e.g.:

(a) amino-9',IO-dihydroacridinese.g. Y 3,6-bis(benzylamino)-9,l-dihydro-9rmethylacridine, 3,6-bis(diethylamino)-9-hexyl-9',l0 dihydroacridine,

3,6-bis(diethylamino)-9,10-dihydro-9-methylacridine, 3 ,6-bis diethylamino) -'9, l0-dihydro-9-phenylacridine, 1 3,6-diamino-9-hexyl-9,10dihydroacridine, 3 6-diamino-9, l0-dihydro-9.-methylacridine, 3 ,6-diamino-9, 10-dihydro-9-phenylacridine, 3, 6-bis dimethylamino) -9-hexyl-9, 10-dihydroacridine, and 3,6-bis (dimethylamino)-9,10 dihydro-9-methylacridine. aminodihydrophenazines e.g. 3 ,7 -bis benzylethylamino) -5 IO-dihydro-S-phenylphenazine, 3 ,7-bis (diethylamino) -5-hexyl-5,10-dihydrophenazine, 3,7-bis(dihexylamino)-5,10-dihydrophenazine, 3,7-bis(dimethylamino)-5-(p-chlorophenyl)-5,10-

dihydrophenazine, 3,7 -diamino-5- (o-chlorophenyl) -5,10-dihydrophenazine, 3,7-diamino-5,lO-dihydrophenazine, 3,7-diamino-5 l0-dihydro-S-methylphenazine, 3,7-diamino-5-heXyl-5,IO-dihydrophenazine, 3,7-bis(dimethylamino)-5,10-dihydrophenazine, V 3,7-bis(dimethylamino)-5,10-dihydro-5-phenylp phenazine, and

3,7-bis(dimethylamino)-5,10-dihydro-5-methylphenazine. (c) aminophenothiazines e.g.

3 ,7-bis (dimethylamino) -phenothiazine, 3,7-bis(dimethylamino)-4, 6-dimethylphenothiazine, 3,7-bis(diethylamino)-2,8-dimethylphenothiazine, 3 ,7-bis (dimethylamino) -4-nitrophenothiazine, 3,7-bis(dibutylamino)-phenothiazine, 3-diethylamino-7-dimethylaminophenothiazine, 3-dimethylamino-7-N-benzyl-N-methylaminophenothiazine, and 3,7-bis(N-benzylaN-ethylamino)-phenothiazine. aminophenoxazines e.g. 3,7-bis(dimethylamino)-phenoxazine, 3,7-bis(diethylamino)-phenoxazine, 3,7-bis(dibutylamino)-phenoxazine, 3-diethylamino-7-dimethylamino-2-methylphenoxazine, 3-dimethylamino-7-dipropylaminophenoxazine, 5-dimethylamino-9-diethylamino-12H- benzo[a]phenoxazine, S-dibenzylamino-9-diethylamino-l2H- benzo[a]phenoxazine, and 5,9-bis(diethylamino)-12H-benzo[a]phenoxazine.

Preferably used oxidizable compounds are volatilizable e.g. between a temperature of 60' to 140 C.

The light-sensitive sheets used according to the present invention contain at least one biimidazolyl compound in a ratio from 2 to 5 mole to 1 mole of reducing agent. Preferably the biimidazolyl compound is applied in an amount of 0.5 to 2 g. per sq.m., but the amount can be adapted according to the requirements of the copying process and the kind of reductor and reducible substance.

For the preparation of the above described intermediate sheet the biimidazolyl compound and reducing agent which is transferable by heat in volatilized or molten state, are applied together from a solution or dispersion preferably in the presence of a film-forming binding agent.

As binding agent for the photosensitive layer all kinds of natural, modified natural and synthetic resins can be used, e.g. proteins such as gelatine, cellulose derivatives, e.g. a cellulose ether: such as ethylcellulose, cellulose esters, carboxymethylcellulose, alginic acid and derivatives, starch ethers, galactomannan, polyvinyl alcohol, poly-N- vinylpyrrolidone, polymersderived from u,/3-ethylenically unsaturated compounds, e.g. homoand co-vinyl polymers such as polyvinyl chloride, copolymers of vinyl chloride and vinyl acetate partially saponified polyvinylacetate, copolymers of acrylonitrile and acrylamide, polyacrylic acid esters, polymethacrylic acid esters, or polyethylene.

The photosensitive material may consist of a self-supporting sheet by using a film-forming binding agent to attain that result, or may comprise a photosensitive layer applied to a support. Suitable supports are, e.g., paper supports of which glassine paper is a preferred one, and resin supports known in silver halide photography. It is also possible to apply the photosensitive material to glass or metal plate or to a support from which it can be stripped OE and transferred to a permanent support.

A receptor material used in conjunction with the photosensitive material contains a substance that is a reactive component in a colour reaction with the reducing compound contained in the photosensitive sheet.

Such substances belong to a wide diversified group of chemicals so that it is practically impossible to characterize them by a particular chemical structure.

A practical test that can be used to know whether a particular reducible compound used in a receiving sheet is suited or not to produce a visible colour change is to heat the elected reaction partners in one of the above binding agents or an inert solvent beyond a temperature of 60 C. with a particular reaction partner to be used in the receiving sheet, and to take notice, e.g. between and C. of the degree of colour change in the layer or test tube.

A relatively high reactivity of a particular reducing agent with the photoexposed biimidazolyl compound is important to obtain clear copies onthe receptor sheet Within a suitable exposure and processing time.

Here again a practical test will make it possible to choose a proper combination of reducing agent and biimidazolyl compound that gives an optimal result.

Reaction partners for at least some of the reducing compounds of the classes (1) to (4) forming a coloured product therewith are listed in the following Groups (I), (11), (IE) and (IV).

(I) Heavy metal compounds especially of metals of the third, fourth and fifth main group as well as of the Ist, the IInd, the VIth, the VHth and the VIlIth auxiliary group of the Periodic Table, e.g. compounds of the following heavy metals: cadmium, mercury, iron, cobalt, nickel, copper, silver, gold, bismuth and thallium. Especially suitable are salts of these metals with long chained aliphatic carboxylic acids, e.g. nickel stearate, cobalt palmitate, iron stearate, the addition compound of bis? muth nitrate with an amine, e.g. triethanolamine. Particularly suited are noble metal compounds e.g. silver compounds, which under the conditions of the copying process of the present invention are extremely nonlight-sensitive, e.g. the silver salts of aliphatic carboxylic acids with a thioether group such as those described e.g. in the British patent specification 1,111,492 filed Aug. 13, 1965 by Agfa A.G., or silver salts of longchained aliphatic (preferably at least C carboxylic acids such as silver behenate, silver palmitate, silver stearate and others.

On applying the above mentioned heavy metal compounds in general brown to black copies are obtained. The image consists of the metal in question and/ or of a reaction product of the transferred image forming compound.

(H) Colour couplers with which the transferred reducing compounds by oxidative coupling react image-wise to dyestuffs, (e.g. suitable couplers for arylamines are described in the United Kingdom patent specification 1,160,224, filed Dec. 14, 1965 by Gevaert-Agfa N.V.).

(III) Diazonium salts for coupling with phenols or naphthols that contain e.g. an amino group, so that coloured compounds are formed as are known from diazotype recording.

(IV) Leucophthalocyanine: As far as leucophthalocyanines were not prepared from ready phthalocyanines, or could not be synthesized therefrom, they are also designated as phthalocyanine preproducts. This term has been employed e.g. in the article of B. R. A. Brooks, J. G. Burt, B. F. Skiles and M. S Whelen, J. Org. Chem., 24, 383 (1959). In the related chapter of Ullmans 'Encyklopadie der Technischen Chemie, 34th edition, vol. 13 the term phthalocyano metal complexes has been used for the same types of substances for which in connection with the present invention the term leucophthalocyanines has been used. The latter term is explained e.g. in the US. patent specification 2,772,285 of Robert A. Brooks, issued Nov. 27, 1956. In this specification it relates only to leuco copper phthalocyanine, but also applies to the corresponding complexes with other phthalocyanine-binding metal. According to this specification leucophthalocyanines are colourless or but light coloured products, in which the phthalocyanine frame already is developed completely, and that can be converted to phthalocyanines by a reduction process. In this reduction process constituents can be split off occasionally simultaneously, which constituents are comprised by the molecule of the leucophthalocyanine and not by the phthalocyanine. The preparation of such leucophthalocyanine can occur e.g. if first of all a phthalocyanine, e.g. a metal free phthalocyaniue or CuPc (Pc=phthalocyanine), NiPc, CoPc or ZnPc are prepared, and thereupon are provided of additional ligands under oxidative conditions, or if a reaction mixture which is suited in itself for the preparation of the phthalocyanine, is heated below the temperature required therefore is reached, or if the reduction potential necessary for the formation of the phthalocyanine is not applied.

Especially suited are metal containing leucophthalocyanines for the metal free leucophthalocyanines are relatively instable. Especially favourable are the very stable and little coloured leuco-cobalt-phthalocyanines.

To be mentioned especially are leuco-cobalt-phthalocyanines described e.g. in Zeitschrift fiir Angewandte Chemie, 68, 145 (1956), such as e.g. the phthalocyaninecobalt-ethylenediamine complex. Instead of ethylene diamine other diamines or polyamines can be built in as ligands, such as propylenediamine-(1,2) and propylenediamine-(1,3), mono-ethylpropylenediamine-( 1,3 hydroxyethylethylenediamine, N-methyl-N-fl-hydroxyethylpropylenediamine, N,N'-diethyl-ethylenediamine, N,N-di-(fi-aminoethyl)-ethylenediamine, N,N'-di(fl-aminoethyl)-ethylenediamine, N,N-di[ 3-(fi-aminoethyl)-aminoethyl]-amine or also monoamines such as 3-(2-ethylhexyloxy)-propylamine(1) or stearylamine. The solubility properties of the corresponding leuco-cobalt phthalocyanine depend on the nature of the built in amine.

According to another embodiment of the method according to the present invention a partner for a colour forming reaction in the receiving layer is absolutely superfluent. This applies for the image-forming phenols or naphthols, which on heating with themselves or in the 12 presence of aerialoxygen yield sufficiently coloured compounds. In this case simple uncoated paper stock can be used as receiving material.

In addition to the actual image-forming reaction partners the image-receiving layers may contain further additives which ameliorate the colour tone e.g. 1-(2H)-phthalazinone, as toner, and which accelerate the reaction for the formation of the image substance, e.g. sterically hindered phenols that on heating become reactive partners in the reduction reaction e.g. 2,4,6-tri-tert.butylphenol. Suitable image-receiving layers are known already e.g. from the U8. patent specifications 3,094,417 of Wesley R. Workmans, issued June 18, 1968, 3,094,619 of Edwin A. Grant, Jr., issued June 18, 1963 and 3,094,620 of John L. Reitter, issued June 18, 1963 and in the German patent specifications 895,101 filed Nov. 10, 1944 by I. G. Far-benindustrie; 1,003,577, filed Feb. 11, 1955 by Agfa A.G.; 1,159,758, filed Sept. 9, 1962 by Agfa A.G.; 1,004,- 043, filed Feb. 7, 1955 by Agfa AG. and 1,165,410, filed Sept. 15, 1962 by Agfa A.G., the Dutch patent specification 277,086 filed Apr. 11, 1962 by Gevaert Photo- Producten NV. and the Belgian patent specifications 614,064, filed Aug. 20, 1962 by Gevaert Photo-Producten NV. and 609,057, filed Apr. 12, 1962 by Gevaert Photo-Producten NV.

For the exposure of the light-sensitive layers according to this invention the usual light source for copying purposes can be used here e.g. mercury lamps, iodine quartz lamps or incandescent lamps. The inherent spectral sensitivity of the photo-sensitive materials depends on the nature of the biimidazolyl compounds used. Most biimidazolyl compounds are sensitive to ultraviolet light of a wavelength below 300 nm. The spectral sensitizability of said compounds makes it possible, however, to use visible light for the exposure step.

A direct exposure as well as a contact reflex exposure can be applied, reflex exposure being particularly interesting for the reproduction of graphic originals having lightabsorptive image areas on an opaque reflecting background.

Transfer of image forming compounds from the unexposed areas of the light-sensitive layers in the imagereceiving layer occurs preferably at a temperature, comprised between and 200 C. Heating can occur e.g. by conveying the exposed light-sensitive layer in contact with an image-receiving layer over hot plates or rollers or by irradiation with infrared light. The most favourable temperature and time of heating of course depends on the nature of the image-forming compound to be formed and can be obtained by few simple tests.

As spectral sensitizing agent for the photosensitive material according to this invention practically a number of compounds are suited, which also have been used for the spectral sensitization of silver halide emulsion layers. These are preferably cyanine dyes, merocyanines, styryl dyes and rhodacyanine of all sorts, e.g. as described by F. M. Hamer. The Cyanine Dyes and related Compounds, 1964, e.g. as described on pages 90, 100, 433, 502 and 511.

In this respect methine dyes according to the three following general Formulae A, B or C are preferably used.

(A) Z Ilia) Z CH=C m-l--on (Y) n I (Y!) n X- wherein:

each of Z and Z represents an oxygen atom or a N-R,

group wherein R represents an alkyl group or a sub- 3 represents hydrogen or a lower alkyl group e.g. methyl or ethyl, 7

each of R and R represents a substituent of the type contained in cyanine dyes on the cyanine nitrogen atom, e.g. an alkyl group such as methyl, ethyl, propyl,

isopropyl, butyl, isobutyl including a substituted alkyl group such as fi-hydroxyethyl, B-acetoxyethyl, carboxymethyl and carboxyethyl as described in the German patent specification 704,141, filed Mar. *9, 1938 by I. G. Farbenindustrie A.G., sulphoalkyl asdescribed in the United Kingdom patent specification 742,112, filed Oct; 23, 1952 by Agfa Farbenfabriken Bayer), such as sulphoethyl, sulphopropyl, sulphobutyl, sulphatoalkyl as described in the French patent specification 1,149,769, filed May 14, 1956 by Veb Filmfabrik Agfa Wolfen, such as sulphatopropyl and sulphatobutyl, the group A-CO OBSO -OH wherein A and B have the same significance as set forth in United Kingdom patent specification 886,271, filed Iune ZO, 1957 by Gevaert Photo-Producten 'N.V. such as a sulphocarbomethoxymethyl group, a w-sulphocarbopropoxymethyl group, a w-sulphocarbobutoxymethyl group, a p (w-tsulphocarbobutoxy) benzyl group, the group AW-NHVB wherein A, W, V and B have the same significance as set forth in United Kingdom patent specification'904,332, filed July 5, 1957 by Gevaert Photo-'Producten N.V. such as a N-(methylsulphonyl) carbamyl methyl group, 7 (acetylsulpharnyl)-propyl, a 6- (acetylsulphamyl) butyl group,

the group t H r 'wherein A has the same significance as described in 'the United Kingdom patent specification 886,270, filed June 24, 11957 by Gevaert Photo-Producten N.V., an aralkyl group such as a benzyl group or a substituted aralkyl group such as carboxybenzyl and sulphobenzyl, an aryl group such as phenyl or a substituted aryl group such as carboxyphenyl, a cycloalkyl group such as cyclohexyl or an allyl group,

each of Y and Y represents a substituent having an elecgroup wherein R ha's'the same significance as described above,

m is a positive integer 1, 2 or 3, I n is a positive integer indicating the number of substituents on the benzene nucleus, and

X is an anion e.g. Cl-, Br, 1, C10;, CH 'SO; or

moQ- s Olbut is not present when the R group contains already anv anionic part ,(betaine-structure) e.g. -tSO R represents an alkyl group or a substituted alkyl group e.g. a C C alkyl group, such as methyl, ethyl, npropyl, n-butyl, benzyl, phenylethyl, a cycloaliphatic group, an unsaturated aliphatic group, e.g. allyl, or an aryl group e.g. a mononuclear aromatic group of the benzene series such as phenyl, or 0-, mor p-tolyl,

each of L L L and L represents a methine group, or

a substituted methine group, e.g. a methine group substituted with a lower alkyl group,

Z represents the atoms necessary to complete a heterocyclic nitrogen-containing nucleus comprising 5 to 6 atoms in the heterocyclic ring such as those of the thiazole series (e.g. thiazole, 4-methylthiazole, 4-phenylthiazole, S-methylthiazole, S-phenylthiazole, 4,5-dimethylthiazole, -4,5-diphenylthiazole, 4-(2-thienyl)-thiazole), those of the benzothiazole series (e.g. benzothiazole, 4-chlorobenzothiazole, 5-chlorobenzothiazole, 6-chlorobenzothiazole, 7-chlorobenzothiazole, 4-methylbenzothiazole, S-methylbenzothiazole, 6-methylbenzo thiazole, S-bromobenzothiazole, 6-bromobenzothiazo1e, 4 phenylbenzothiazole, 5 phenylbenzothiazole, 4-methoxybenzothiazole, S-methoxybenzothiazole, '6-methoxybenzothiazole, 5 iodobenzothiazole, 6 iodobenzothiazole, 4 ethoxybenzothiazole, 5 ethoxybenzothiazole, 4,5,6,7 tetrahydrobenzothiazole, 5,6 dimethoxybenzothiazole, 5,6-dioxymethylenebenzothiazole, S-hydroxybenzothiazole, 6-hydroxybenzothiazole, 5,6-dimethylbenzothiazole), those of the naphthothiazole series (e.g. naphtho[2,1-d]thiazole, naphtho[l,2-d]thiazole, 5 methoxynaphtho[1,2-d]thiazole, 5 ethoxynaphtho- 1,2-d] thiazole, 8-methoxynaphtho [2,1-d] thiazole, 7- methoxynaphtho[2,1-d]thiazole), those of the thianaphtheno[7;6-d1thiazole series (e.g. 7-methoxythianaphtheno[7,6-d]thiazole), those of the oxazole series (e.g. 4-1nethyloxazole, S-Inethyloxazole, 4-phenyloxazole, 4,5-diphenyloxazole, 4-ethyloxazole, 4,5-dirnethyloxazole, 5-phenyloxazole), those of the benzoxazole series (e.g. benzoxazole, S-chlorobenzoxazole, S-methylbenzoxazole, S-phenylbenzoxazole, -6-methylbenzoxazole, 5,6 dimethylbenzoxazole, 4,6 dimethylbenzoxazole, S-methoxybenzoxazole, 6-methoxybenzoxazole, S-hydroxybenzoxazole, 6-hydroxybenzoxazole), those of the naphthoxazole series (eig. naphtho[2,1-d]oxazole, naphtho[1,2-d]oxazole), those of the selenazole series (e.g. 4-methylselenazole, 4-phenylselenazole), those of the benzoselenazole series (e.g. benzose'len azole, 5-chlorobenzoselenazole, S-methoxybenzoselenazole, 5 hydroxybenzoselenazole, 4,5,6,7 tetrahydrobenzoselenazole), those of the naphthoselenazole series (e. g. naphtho [2,1-d] selenazole, naphtho[1,2-d]selenazole), those of the thiazoline series (e.g. thiazoline, 4 methylthiazoline, 4 hydroXymethyl-4-methylthiazoline, 4,4-bis-hydroxymethylthiazoline, 4-acetoxymethyl- 4 methylthiazoline, 4,4 bis-acetoxymethylthiazoline), those of the oxaline series (e.g. oxazoline, 4-hydroxymethyl-4-methyloxazoline, 4,4-bis-hydroxymethyloxazoline, 4-acetoXymethyl-4-methyloxazoline, 4,4-bisacetoxymethyloxazoline), those of the selenazoline series (e.g. selenazoline), those of the 2-quinoline series (e.g. the quinoline, 3-methylquinoline, S-methylquinoline, 7-methylquinoline, 8-methylquinoline, 6-chloroquinoline, 8-chloroquinoline, '6-methoxyquinoline, 6- ethoxyquinoline, 6-hydroxyquinoline, 8-hydroxyquinoline), those of the 4-quinoline series (e.g. quinoline, 6-methoxyquinoline, 7-methylquinoline, '8-methylquinoline), those of the pyrrolidine series (e.g. l-ethyl-pyrrolidine or l-methyl-pyrrolidine, those of the 3,3dialkylindolenine series (e.g. 3,3 -dimethylindolenine, 3,3,5 trimethylindolenine, 3,3,7 trimethylindolenine), those of the pyridine series (e.g. pyridine, S-methylpyridine), those of the benzimidazole series (e.g. lethylbenzimidazole, l-phenylbenzimidazole, l'-ethyl-5- chloro 6 bromobenzimidazole, l-ethyl-S-phenylbenzimidazole, 1-ethyl-S-fluorobenzimidazole, 1-ethyl-5,6- difluorobenzimidazole, 1 ethyl-5-cyanobenzimidazole, 1(,8-acetoxyethyl) 5 cyanobenzimidazole, l-ethyl-S- chloro-6-cyanobenzimidazole, 1-ethyl-5-fluoro-6-cyanobenzimidazole, 1-ethyl-5-acetylbenzimidazole, l-ethyl- S-chloro-6-fiuorobenzimidazole, 1-ethyl-7-carboxybenzimidazole, 1-ethyl-7-carboxybenzimidazole, l-ethyl-S- carbethoxybenzimidazole, l-ethyl 7 carbethoxybenzimidazole, l-ethyl 5 sulphamylbenzimidazole, or 1- ethyl-5-N-ethyl-sulphamylbenzimidazole,

n represents 1 or 2,

m represents 2 or 3, and

each of P and Q represents an electronegative substituent, or

P and Q together represent the necessary atoms to close a cyclic ketometh'ylene nucleus e.g. an imidazolonethione or rhodanine nucleus.

wherein each of R' and R' represents an alkyl group, e.g. a (C -C alkyl group or an aralkyl group, e.g. a benzyl group, each of L L L and L represents a methine group, including a substituted methine group,

Ar represents a bivalent aromatic nucleus, e.g. a phenylene group,

p represents 1 or 2,

q represents 2 or 3, and

Z represents the atoms necessary to complete a heterocyclic nitrogen containing nucleus comprising 5 to 6 atoms in the heterocyclic ring e.g. a pyridine nucleus, a thiazole nucleus, an oxazoline or a quinoline nucleus.

The sensitizing agents may be added to the photosensitive composition in a suitable solvent such as short chained aliphatic alcohols or aqueous systems. The concentration of the spectral sensitizing agent(s) may vary within wide limits. In general amounts comprised between 0.05 and 0.3 mole/per mole of biimidazolyl compound have been proved as sufficient.

The most suitable sensitizing agents for a particular biimidazolyl compound can be determined by means of the usual sensitometric tests, without difficulty by those skilled in the art.

By the addition of sensitizing agents not only an increase of sensitivity is reached but also a marked increase of the general sensitivity, which is desirable for obtaining shorter times of copying. By the possibility of sensitization of layers according to this invention also for the red and green region of the spectrum it is possible not only to copy coloured originals in an unobjectional way but also to prepare copies in natural colours by a suitable choice of the image forming systems which yield dyestuffs in the substractive selection colours.

In order to obtain stable positiveidirect legible copies of graphic originals having differentially light-absorptive image and background areas the photo-oxidizing biimidazolyl compound is preferably used in combination with a volatilizable reducing agent in a sheet, which is the so-called intermediate sheet, a preferred reducing agent for that purpose is 4-methoxynaphthoL- Said sheet co-operates after its information-wise electromagnetic irradiation with a receiving material, the socalled receptor sheet that contains a reducible substance, e.g. silver behenate, for producing a colour reaction with the reducing agent treansferred by heat after the information-wise exposure of the intermediate sheet.

It is possible to obtain copies of transparent as well as of opaque originals in a unitary photothermosensitive copy sheet by using e.g. on a thin transparent paper-like backing a thin coating comprising said reducible substance, kept out of direct chemical contact with respect to the reducing agent and the photo-oxidizing biimidazolyl compound by means of a thin non-transparent highly pigmented vapour-permeable binder layer the binding agent of which is not soluble in the solvent from which the photosensitive top-coat is applied.

The unitary photothermosensitive copy sheet yields when applied in a reflux exposure technique a copy that is directly legible through the rear side of the transparent support.

A pigment such as titanium dioxide and zinc oxide having an average grain size of 5 to 1 when applied in an ethyl cellulose binder allow the vaporized reducing agent e.g. 4-methoxynaphthol to pass through the vapour permeable interlayer and to react with the reducible substance e.g. silver behenate.

The permeable layer may alternatively be replaced by a normally impermeable thin coating of a-fusible filmforming material which melts and becomes compatible with the underlaying binder medium for the reducible substance. (See for such technique and suitable substances the United Kingdom patent specification 1,184,054, filed Apr. 5, 1966 by Gevaert-Agfa N.V. and the US. patent specification 3,223,838 of Shoichiro Hoshino and Akira Kato, issued Dec. 14, .1965.)

.Heat may be applied by conventional thermographic front-printing procedures using infra-red radiation. Replacing the printed original with a continuously infrared-absorptive black paper, plate, roller and irradiating that absorptive material in contact with the photothermosensitive sheet causes overall reproducible heating.

It is of course possible to use other kinds of energy sources to produce heat, of which electrical resistance heating and high frequency current heating and induction heating are a few examples.

Instead of transferring the reducing agent in volatilized state it is possible to transfer it in a fusible medium, e.g. a fusible waxy or resinous medium. Transfer can be speeded up by using a solvent causing some swelling as described in the United Kingdom patent specification 1,135,371, filed Jan. 7, 1966 by Agfa-Gevaert A.G. Heat transfer of polymer substrata without solvent swelling is described e.g. in the Belgian patent specification 700,- 472, filed June 26, 1967 by Gevaert-Afga N.V. corresponding with the United Kingdom patent specification 1,195,842, filed June 24, 1966 by Gevaert-Afga N.V.

The following examples illustrate the present invention. Parts are parts by weight unless otherwise indicated.

EXAMPLE 1 A photosensitive intermediate sheet was prepared by coating a glassine type paper base in a ratio of 40 g. per sq.m-. with a solution of the following composition:

Bis[2 (o chlorophenyl) 4,5 diphenyl imidazole] g 10 4-methoxy-1-naphthol g 1 Ethylcellulose g 10 Z-butanone ml v 5 00 The resulting sheet was dried and irradiated for 12 sec. through a positive transparency of a printed text by means of an ultraviolet light source (1000 w..-lamp) placed at a distance of 5' cm. from the intermediate sheet.

Subsequently the irradiated sheet was pressed for 5 sec. with its photosensitive layer. in contact at 125 C. with a'receptor sheet, which is a white paper prepared by coating and drying thereon a continuous thin colour- A photosensitive intermediate sheet was prepared by coating a map overlay tracing paper in a ratio of 50 g. per sq.m. with a solution of the following composition:

Bis[2 (o chlorophenyl) 4,5 diphenyl imidazole] g 10 2,S-di-tert.-but1yl-hydroquinone 1 Ethylcellulose g 10 Chloroform ml 500 After exposure for 15 sec. and transfer contact as described in Example 1 a sharp brown positive print of the original was obtained.

EXAMPLE 3 A transparent subbed polyester film of 0.10 mm. thickness was supplied in a ratio of 30 g. per sq.m. with a solution of the following composition:

Bis[2 chlorophenyl) 4,5 diphenyl imidazole] g 10 p-Phenylenediamine g 1 Cellulose acetate butyrate (half second but ate) 3 l0 Z-butanone m1 500 After image-wise exposure the dried coating was contacted for 5 sec. as described in Example 1 whilst heating at 120-130 C. with a receiving paper sheet the receptor layer of which was prepared from. a solution as described hereinafter.

N-(2,4-dinitrophenyl)-pyridinium chloride ...g.. 5 Saponine g 0.2 Polyoxyethylene hydroxyethylcellulose (marketed under the trade name Cellosize WP 09 by Union Carbide & Carbon, New York) g 1 Water ml 100 A dark-brown positive image on a yellow background was formed. 1

EXAMPLE 4 The intermediate sheet of Example 1 was sensitized to visible light by adding to the coating composition for every 500 ml. 1 g. of 2-(p-dimethylaminostyryl)-benzothiazole as spectra'lly sensitizing agent.

A direct exposure for 3-0 sec. through a positive transparency with a tungsten filament light source of- 1500 w. placed at a distance of 10 cm. from the intermediate sheet made it possible to produce a sharp positive black copy on contact-heating transfer as described in Example 1.

By using as original a black printed text on an opaque white background a reflex exposure yielded after a 15 to 25 sec. irradiation with the same light source a brown positive print on the same receptor sheet.

EXAMPLE s The photosensitive intermediate sheet of Example 3 was sensitized to visible light by adding to every 500 ml. of said solution 1 g. of a spectral sensitizing merocyanine dye containing a rhodanine nucleus and having the following structural formula:

Ton-011T Ts III 0 N 02H gHs EXAMPLE 6 A solution suited for preparing an intermediate photosensitive sheet was prepared as follows:

20 g. of di(2,4,5-triphenylimidazole) were dissolved in 350 ml. of Z-butanone. The pink solution obtained discoloured after a few hours standing at room temperature, an isomerisation according to the following scheme had taken place:

C-N isomer To the discoloured solution the following ingredients were added;

I G. n-Ifropyl gallate 1 10 Ethylcellulose The solution was applied in a ratio of 30 g. per sq.m. onto a glassine type paper base. After drying at room temperature the material obtained was image-wise exposed for 20 sec. in a direct exposure with a 1000 watt U.V. light source placed at a distance of 5 cm. from the photosensitive coating.

A positive brown image was obtained. Y

. 19, EXAMPLE 7 On tracing paper the following composition was coated in a ratio of 40 g./sq.m.:

Di[2-(o-chlorophenyD-4,5-diphenyl-imidazole] g 15 N,N-diethyl-p-phenylenediamine g 1 Ethylcellulose g 10 2-butanone ml 500 After an image-wise exposure with U.V. light for 10 seconds by means of a 1000 w. lamp, the layer was pressed at 120-130 C. for 5-7 seconds on a paper that had been impregnated With the following 2 compositions (A) and (B):

Potassium persulphate g 2 1 N sodium hydroxide solution ml 5 Saponine g 0.5 Polyoxyethylene hydroxyethylcellulose g 0.5 Water ml 45 After drying the following composition (B) was applied thereto.

(B) N-hexadecyl-1-hydroxy-4-chloro-Z-naphthoic acid amide having the formula:

A material was obtained which was then exposed as described in Example 8. A positive, cyan copy was obtained.

EXAMPLE 8 In order to obtain a yellow image on a receiving layer prepared as described in Example 7, the Z-naphthoic acid amide compound of composition (B) was replaced by 1 g. of 'benzoylacetanilide.

EXAMPLE 9 By replacing in the receiving layer N-hexadecyl-lhydroxy-4-chloro-2naphthoic acid amide by 1 g. of pm'trophenyl-methylsulphide a magenta image was obtained.

EXAMPLE 10 If in the light-sensitive composition of Example 7 l g. of 2-(4-dimethylamino-styryl)-quinoline was added for every 500 ml., exposure could be carried out with visible light (1500 watt lamp for -30 seconds) through a transparent original or to an opaque original.

EXAMPLE 11 A U.V. light-sensitive layer was obtained by coating a polyester film or tracing paper with the following composition: i

20 W .As a receiving layer a material comprising silver behenate can be used. A sharp, black, positive image was obtained.

EXAMPLE 12 The material of Example 11 could be used by employing as a receiving layer a paper which had been coated with the following mixture that had been ball-milled for 10 hours:

Mercury(II) stearate g 2 Copoly(vinylchloride vinyl acetate 7 vinylalcohol) (sold under the trade name Vinylite VAGH by Bakelite Corporation g 2 Z-butanone ml After exposure as described in Example 8 a brownish violet image was obtained.

EXAMPLE 13 Example 11 was repeated but the phenothiazine'in the photosensitive material was replaced by phenoxazine. After exposure as described in Example 8 a black image was obtained.

EXAMPLE 14 Example 13 was repeated but mercury(II) stearate was incorporated into the receiving layer. After exposure as described in Example 6 a brown image was obtained.

EXAMPLE 15 A photosensitive intermediate sheet was prepared by coating a glassine type paper base in a ratio of 40 g. per

sq.m. with a solution of the following composition:

Bis[2 (o chlorophenyl) 4,5 diphenyl imid-.

azole] g 10 4-methoxy-1-naphthol g-.. 1 A sensitizing dye listed in the table hereinafter rng 5 Ethylcellulose g 10 2-butanone ml 500 The resulting sheet was dried and irradiated for 2min. through a step wedge having consecutive steps with optical density increments of 0.1.

In the exposure a visible light emitting light source 1500 w.incandescent halogen containing lamp) placed at a distance of 5 cm. from the intermediate sheet was used.

Subsequently to the irradiation the sheet was pressed at C. for 5 sec. with its photosensitive layer in contact with a receptor sheet which is a white paper prepared by coating and drying thereon a continuous thin colourless layer of a ball-milled mixture of silver behenate, phthalazinone as toning agent, 2,6-di-tert.-butyl-4-methylphenol as heat-sensitive reductor, poly-tert.butyl methacrylate as binding agent (3 parts for every 10 parts of silver behenate) and 86 parts of acetone The dried receptor sheet contained per sq.m. an amount of silver behenate equivalent with 0.2 g. of silver per sq.m., 400 mg. per sq.m. of phthalazinone, and 40 mg. per sq.m. of 2,6-di-tert.-butyl- 4-methylphenol.

In each case a positive black wedge print was obtained. 7 In the following Tables A, B and C the first wedge step that is visible reproduced on the receiving material is given for each diflerently sensitized photosensitive intermediate sheet. The higher that number, the higher the sensitivity since it indicates the amount of steps in the photosensitive intermediate sheet, in which the reducing 4-methoxy-1-naphthol has been transformed into anonredu cing state by meansof the photo-exposed dye sensi tized biimidazolyl compound.

TABLE 13 l"\ X s= H I N Sens.

max. Test No Z Y R X Stops (nm.)

1 CH; CHaCE: B a 598 T OHCH=CH- CH 0H: omen: 12115 2..:::::::::::::::::: (3211's (IE-OH 01H; 7 S 7 480 H10 (1: H, H, 3.-.'::.-.:::::::?.::n CH-OH CH; NCH; 9 468 N H,-&H2 4...I:::::;:'.::::::::r:.:': f0],1 OBI-CH CH1 NOaH 11 480 (CH|):OS0:H-N(Ca e)l 5...;T::T.1:..'.T::::.:: /O CH-OH CH; NCgH; 12 4.85

TABLE 0 Table C Conttnucd max. visible Sensi- Test No. Z R; (nm.) step tivity First max. visible e s N(CH OH:OI): 400 a Test No Z R; (nm.) step T "12:7. N C H 420 6 I 1 a a): N

\N 7 ..'r::::: /S' N(CH|CH|CN): 400 6 2 /\/ST N(C'|Hb)s 420 8 T L We claim:

1. A method of recording information comprising the CH 398 6 3 /\/S m steps of (1) imagewise exposing to activating electromagnetic radiation a photosensitive recording element -N comprising a photo-oxidizing biimidazolyl compound that stands in chemically reactive contact with a compound 4 mom), 396 7 having reducing properties, which properties are destroyed by a reaction in the exposed areas of the element with the photo-oxidized bi-imidazolyl compound, (2) uniformly contacting the thus-exposed element with an H 400 7 image-forming compound reactive on heating with said 5 Nw reducing compound to produce a distinctive coloration, and (3) heating the exposed element while in contact with said image-forming compound to produce a visible N image corresponding to the unexposed areas of said element by reaction of the reducing compound in said areas with said image-forming compound, said biimidazolyl compound having the general formula: V

wherein: each of R R and R stands for a carboeyclic orheterocyclic group with aromatic character, said group being free from Zerewitinolf hydrogen atoms and each dotted line circle represents 4 delocalized electrons, and said compound having reducing properties is selected from:

(1) aromatic polyhydroxyl compounds and oxidizable derivatives thereof; (2) aromatic polyamino compounds and oxidizable derivatives thereof; (3) aromatic hydroxyl-amino compounds and oxidizable derivatives thereof; and (4) compounds of the general formula:

wherein:

X represents oxygen, sulphur, -NH-,

-CI-I -CH-=CH, or

and Z and Z each represent the necessary atoms to close a carbocyclic aromatic ring.

2. The method of claim 1 wherein said image-forming compound is uniformly carried on an image-receiving element which is brought into contact with said exposed recording element and upon heating of said exposed element, said reducing compound is transferred from the unexposed areas thereof to said image-receiving element and reacts with the image-forming compound thereon to produce said visible image.

3. The method of claim 1 wherein said reducing compound and said image-forming compound are carried in separate layers on said recording element and upon heating of said element are brought into reactive contact.

4. A method according to claim 1 wherein the biimidazolyl compound corresponds to one of the following isomeric structures:

eral formula:

B D an] I -l- 26 wherein the valencies of the atoms in the' imidazolyl rings, other. than those joining the imidazolyl rings, are satisfied by two conjugated intracyclic double bonds, and wherein A is a substituted phenyl radical of the formula:

wherein R represents a substituent free from active hydrogen atoms and R R and R represent hydrogen or substituents free from active hydrogen atoms or two in adjacent positions taken together form a benzo ring. with the proviso that any substituent ortho to the imidazolyl radical has a sigma consant below 0.7; and B and D are phenyl groups which are unsubstituted or substituted with up to three substituents free from active hydrogen atoms, two of which, in adjacent positions on the phenyl ring, may together form a benzo ring; with the proviso that at least one of the ortho positions in each of the phenyl groups B and D is unsubstituted.

6. A method according to claim 5 wherein the substituents on the phenyl radicals A, B and D are each in alkyl group containing up to six carbon atoms, an alkoxy group containing up to six carbon atoms, a chlorine, bromine or fluorine atom, or on adjacent pairs form together a benzo ring.

7. A method according to claim 1 wherein said compound having reducing properties is volatile between 60 and 200 C.

8. A method according to claim 7 wherein said reducing compound is a phenol or naphthol.

9. A method according to claim 8 wherein said reducing compound is a phenol or napthol having at least two hydroxyl groups directly bonded to the aromatic ring or an ether thereof.

10. A method according to claim 1 wherein said reducing compound is an aromatic hydroxyl-amino compound of the benzene or naphthalene series in which compound a hydroxyl group and an amino group are present in orthoor para-position.

11. A method according to claim 10 wherein the photooxidizable compound is 4 methoxy-l-naphthol.

12. A method according to claim 1 wherein the biimidazolyl compound has been spectrally sensitized.

13. A method according to claim 2 wherein the receiving material comprises a substantially non-light-sensitive noble metal salt.

14. A method according to claim 13 wherein the noble metal salt is a silver salt of an aliphatic carboxylic acid having from 8 to 24 carbon atoms.

15. A method according to claim 14 wherein the silver salt is silver behenate.

16. A photosensitive recording material containing a bi-imidazolyl compound, and in chemically reactive contact with said compound ('1) a phenol or naphthol having at least two hydroxyl groups directly bonded to the aromatic ring or an ether of said phenol or naphthol, or (2) an aromatic hydroxyl-amino compound of the benzene or naphthalene series, in which a hydroxyl group and an amino group are present in orthoor para-position, said bi-imidazolyl compound corresponding to the general formula:

17. A photosensitive recording material according to claim 16 wherein the photo-oxidizable compound is 4- i'nethoxy-l-naphthol. r

18. The recording method of claim 1 wherein said hiimidazolyl compound is present in said element in the amount of about 0.5-2 g./g./sq. m. and said reducing compound is present .in a ratio relative to said bi-imidazolyl compound of about 1:2-5 on a molar basis.

19. The recording material of claim 16 wherein said bi-imidazolyl compound is present in said element in the amount of about 05-12 g./ sq. m. and said reducing compound is present in a ratio relative to said bi-imidazolyl compound of about 1:2-5 on a molar basis.

'28 1 References Cited;-

UNITED STATES PATENTS 3,445,234 5/1969 Cescon et al :71.- 96-90 3,585,038 6/1971 Cjesconet a1. L'.. 9690 5 2,789,904 4/1957 Benbrook et 1, 9649 3,531,286 9/1970 Renfrew 96-114.1

NORMAN G. TORCHIN, Primary Examiner 10 W. H. LOWE, JR., Assistant Examiner- -us. c1. X.R. 

